Gas grilling appliances commonly have rotary valves mounted on the front control panel of the appliance. Each rotary valve has an actuating shaft that passes through the front control panel into the interior of the appliance. The actuating shaft extends inside a hollow valve body located within the appliance and connected to a gas inlet conduit. The external end of the actuating shaft is fitted with a rotary control knob. The rotary control knob may be removed from the actuating shaft by pulling the knob away from the shaft.
The valve body also has a gas outlet conduit connected to a burner. The gas outlet conduit has an injector nozzle comprising a calibrated discharge orifice chosen according to the type of gas to be supplied to the burner, e.g., liquid propane gas (“LPG”) or natural gas (“NG”). The injector nozzle may be spaced apart from the burner inlet by a small distance to allow air to mix with the gas to create a combustible mixture as the gas is fed into the burner. Alternatively, the injector nozzle may extend into the burner inlet, with air entering the burner through holes in burner.
An example of such a rotary valve is disclosed in U.S. Pat. No. 6,520,481. In this patent, the rotary valve has an actuating shaft coupled to a frusto-conical regulating plug or valve plug. The plug is configured to pivot through a 270-degree angle to supply gas at varying rates of flow to the burner.
In this type of rotary valve, the actuating shaft or control knob has a pin that limits the angular travel of the shaft. The pin is guided by a groove cut in the valve body or in the front control panel. The groove limits the angular travel of the actuating shaft or control knob, and thus the angular travel of the regulating plug. As the pin moves within the groove, the plug pivots, exposing an opening in the plug of varying cross-section to the gas inlet conduit and thus regulating the flow of gas from the inlet conduit to the burner.
Like the discharge orifice, the opening in the regulating plug is calibrated for a particular type of gas, e.g., LPG or NG. This presents a challenge when a user wants to convert the gas grilling appliance from one type of gas to another. While it is relatively easy to replace the injector nozzle or to mount an additional injector nozzle on the gas outlet conduit, as is described in U.S. Patent Application Publication No. 2008/0138749, changing the calibration of the opening in the regulating plug for different gases is more complicated.
For example, in U.S. Pat. No. 5,009,393, a sleeve is inserted in the inner chamber of the regulating plug. The area of the opening in the regulating plug is adjusted by rotating the sleeve, thus modifying the uncovered area of the opening. This solution suffers from the disadvantage that, to rotate the sleeve, the user has to transmit a precise turn to the sleeve using a tool that the user has to insert in an opening in the actuating shaft.
In U.S. Patent Application Publication No. 2008/0138749, the grilling appliance has a plurality of rotary valves, each of which includes a pair of interchangeable control knobs. An integral lug is formed on the back side of one of the interchangeable control knobs of each pair of knobs, facing the control panel, for use with NG (“the NG control knob”); the other one of the interchangeable control knobs, for use with LPG, does not have such a lug (“the LPG control knob”). When the NG control knob is placed on the valve shaft, the integral lug is received in an arcuate slide groove that is formed in the control panel around the opening for the valve shaft. One end of the slide groove functions as a stop for the integral lug on the NG control knob and, hence, limits the rotation of the NG control knob. Since the LPG control knob lacks such a lug, its rotation is limited only by the valve itself. The user chooses the control knob based upon the type of gas to be used. Although this solution avoids the need to use a tool as in U.S. Pat. No. 5,009,393 discussed above, it suffers from the disadvantage that, to convert a grilling appliance from one type of gas to another, the user purchase and install a whole new set of control knobs, which can be costly and wasteful.
Accordingly, there is a need for a conversion kit for a gas grilling appliance having rotary valves, the conversion kit comprising a regulating device configured to allow a user to convert the appliance from one type of gas to another while avoiding the problems discussed above. The present invention satisfies this and other needs, and provides further related advantages.